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Misconception
It is a popular misconception that sharks eat people, thanks to popular movies like "Jaws." Although some sharks attack people, they usually just take a bite and spit the person back out. Sharks attack their prey from below. People swimming on the ocean surface, especially if they are on surfboards, appear similar to seals, which sharks like to eat. Species known to attack humans include the white shark, bull shark and tiger shark.
Baleen Sharks
Baleen sharks lack the distinctive knife-like teeth associated with sharks. They instead feed by using baleen, a type of fleshy filter. Instead of expending large amounts of energy to hunt prey or find carrion, baleen sharks merely open their massive mouths, gulp water and filter out plankton, or tiny sea plants. The whale shark or Rincodon typus is the world's largest fish, averaging 40 feet in length and weighing in at a whopping 20 tons.
Toothed Sharks
Most shark species have teeth instead of baleen. These teeth prove effective for grabbing and gulping prey. Juvenile sharks eat fish or crustaceans smaller than themselves. Adult sharks eat large fish, including other sharks, seals and sea lions, penguins, sea birds, lobsters, crabs, stingrays, sea turtles and whatever carcasses they come across. One species called a cookie-cutter shark or Isistius brasiliensis takes chunks out of whales or very large fish like tuna but does not kill the prey outright. Its teeth are behind a strong sucker mouth.
Intrauterine Cannibalism
Some species of shark, such as the sand tiger shark or Carcharis taurus, are literally born killers. Instead of laying eggs, females of this species give birth to one large pup. However, her womb held many fertilized and unfertilized eggs. The shark pups eat the infertile eggs and then each other until only one is left. The survivor's prebirth experience gives it a much better chance for survival after leaving the protective body of its mother.